The Application Of Multiple Control Strategy In Tobacco Re-drying Process

Based on the background of the control system of the tobacco re-drying process, the control strategy of the tobacco re-drying process is discussed in this paper. From the analysis of the past data, double control and modified double control didn’t control well, because this complex industrial process is nonlinear, time-varying, hysteresis and is a large scale system. To the control of the production process indicators, the control strategy is lack of the control precision and show slow reaction and so on. Therefore, on the basis of the double control, this paper try to use the triple control strategy to solve the problems, combining with the classical PID algorithm and advanced predictive PI control algorithm. The paper also gives the control effect simulation analysis of which the double and triple control applied to the first order of pure lag link.For the problem that the outlet moisture content control provides low control accuracy and the regulating valve can’t regulate because of saturation in the process of tobacco re-drying. A triplex control strategy which is capable of controlling multiple manipulated variables is designed in the following: As the main controlled object, the regulation of high pressure water pump in the resurgence section has a direct and quick effects on the outlet moisture. As the first subsidiary controller, the predictive PI algorithm is applied to the main controller. The regulation of mixed water changes the humidity in resurgence section slowly. The proportional-integral control algorithm is applied to the first subsidiary controller. In order to prevent the open degree of the high pressure pump and the mixed water regulating valve from saturating, the set value of the moisture contents in cooling section is chosen as the second subsidiary controlled object to affect indirectly on outlet moisture content. The whole system is operated under the combination of the hardware and software, connecting the OPTO22 components which include CPU, I/O port and so on. The design of the controller is realized under the OPTO22 development environment, using MATLAB SIMULINK to simulate the transfer function in the actual industrial process, and form a complete set of system with the actual development tools. By adjusting the parameters of the controller and observing the output curve, to realize the optimal running effect.Finally,the author design a set of PC system through OPTO22 PAC assembly. It can remotely adjust the parameters, monitor the change of the output in real time, and increase the engineering application of this control strategy. According to the practical results, this control strategy can regulate the outlet moisture content precisely, and concert the open degree of the regulating valves promptly. It provides a new idea for industrial production, improves the automation level of the whole production line and has a great value to the industrial application.